IMU In-Motion Alignment Without Benefit of Attitude Initialization

Robert M. Rogers

Abstract:	The problem addressed in this paper is the establishment of local level wander azimuth navigation and body reference frames for an Inertial Navigation System (INS) based on outputs of an Inertial Measurement Unit (IMU) without the use of initial attitude information. The availability of initial position and velocity in a geographic or earth-centered reference frame is assumed. This information is consistent with that available from a Global Positioning System (GPS) receiver; however, in this paper an aircraft navigation systems’ data is used instead. The formulation presented does not assume that the IMU’s host vehicle heading and velocity are along the same direction. Alignment is accomplished using a Kalman filter algorithm implemented with an INS system error model formulated for large heading errors and using position measurement updates. This algorithm provides estimates of navigation frame referenced velocity, wander azimuth and body attitude errors that are used to continuously correct the on-going navigation solution calculations. The performance of the alignment algorithm is evaluated using actual IMU and aircraft data from fight tests.
Published in:	Proceedings of the 1997 National Technical Meeting of The Institute of Navigation January 14 - 16, 1997 Loews Santa Monica Hotel Santa Monica, CA
Pages:	945 - 954
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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